Your exhaust gases might sound like a waste that you shouldn’t concern yourself with. Not true. Even though it’s waste, a leak that doesn’t let it flow all the way to the exhaust pipe tip at the rear of the car is bad news.
Your exhaust system consists of different connections and components. It consists of metal components that could rust through and create leaks.
Additionally, since it sits down low, there are chances of getting some part of the exhaust system scratched or punctured when driving over debris.
Symptoms of an Exhaust Leak
There are different hints on whether you have an exhaust leak or not. Some of the most fundamental include:
An Abnormally Loud Exhaust
Every component in your exhaust system plays a role in lowering engine noises. The muffler, catalytic converter, and resonator have a more significant impact on how loud your car gets.
A leak that lets out exhaust gases before passing through one of these components will make your car sound louder. It will have a sound rattling or obnoxious sound.
The noise is louder if the leak is big and closer to your engine, meaning it bypasses more silencing components of the exhaust system.
Ticking, Puffing, and Hissing Sounds
Just like the vacuum in your car’s intake, the exhaust side is under some pressure. The difference is its positive pressure, not harmful like the intake.
Despite this, the pressure is enough to push gases through cracks, holes, and gashes. As the gases go by, they will create a tell-tale puff, rattle, or hiss, depending on how stiff the metal or gasket they are leaking around is.
The intensity and frequency of the hiss change depending on how hard you rev the engine.
Bad Gas Mileage
Gas mileage takes a hit if the leak is before your oxygen sensor. This throws off the sensor’s readings making it send flawed information to the ECU.
This could trick a car running normally into thinking it’s lean. Consequently, the ECU instructs fuel injectors to send in more fuel.
This increases your gas mileage considerably. It could, at times, have other detrimental impacts on your motor.
Metal Vibrations
Besides just creating a whistling noise when escaping, exhaust gases can make loose metal parts around leak points vibrate.
This will cause annoying metal vibrations at different parts of the car.
Carbon Build Up Where You Don’t Expect it.
Carbon is dark and hard to miss. However, it has no place in your engine bay or under your car. It should only occur at the tip of the exhaust pipe.
However, leaks make carbon accumulate at or around the point it is leaking at. Inspect your entire exhaust system looking for black sooty spots. If you find one, signs are you have a leak at or around that spot.
Exhaust Fumes Smell in the Car
A compromised exhaust system leaks out fumes before they reach the rear of the car. Exhaust pipes sit at the back of your vehicle for a reason – to channel these gases out and away from occupants.
Usually, you shouldn’t smell these fumes at all (unless you are standing behind the car)
If you do, it means there is a leak somewhere in the engine bay or under the car. This could let the fumes seep up and into the cabin, where you’ll pick them up while parked or driving.
Visible Cracks or Holes in the Exhaust System
Finally, you can observe holes, dents, and gashes on your exhaust system if you are keen.
Get the car on a lift and observe all components of the exhaust system. Visible holes are due to impact damage or rust.
Please pay close attention to any spots that seem to be suffering from such forms of stress as they could be leaking.
Before looking at different causes of an exhaust leak, we first understand what the exhaust system does and what it is made of.
Parts of an Exhaust System
In most cases, the exhaust system is a set of steel pipes designed to handle the heat and stress of staying exposed under the car.
However, modern cars have more on their exhaust system. They have added more parts to the traditional exhaust system. A typical exhaust system is made of:
The Exhaust Manifold
The first step in the exhaust system is the exhaust manifold. It bolts onto the engine block and gathers exhaust gases from different cylinders before channeling them through one or more pipes.
This part uses a couple of gaskets and bolts to create a tight seal and collect all the gas before shuffling it away.
A Catalytic Converter
This is a new system mandated by regulation in many countries. Its work is cleaning most of the harmful emissions from your engine before releasing them into the atmosphere.
A catalytic converter uses rare metals to catalyze carbon monoxide, nitrous oxides, and other hydrocarbon wastes into safer byproducts like carbon dioxide, nitrogen, and water vapor.
The Resonator
A resonator is an echo chamber added to the exhaust system to modify your exhaust’s sound. It retunes the exhaust gases flowing through and can be a great way to make your car sound different.
A Muffler
Further down the system is a muffler. The size and efficiency of a muffler vary depending on the tune of the car.
A muffler’s role is muting the loud noises from your engine. Typical families or luxury cars have better mufflers that stifle most of the sound from the engine.
Tuned or performance cars have a muffler that lets some of the modified sounds from the resonator (if you have it) through to give your vehicle a meaty growl.
The Tailpipe
The tailpipe is a traditional part of the exhaust system. It is the last piece of the puzzle that releases exhaust gases out in the open. It’s usually a short stub attached to a muffle or a resonator.
Oxygen Sensors
Oxygen sensors are additional components that you’ll find in all fuel-injected cars. They read the composition of exhaust gases and send that information to the ECU.
The ECU can use this information to determine if your engine is running lean or rich. Moreover, comparing the readings of two oxygen sensors (an upstream and a downstream oxygen sensor) lets it determine if you have an active catalytic converter or not.
Traditional Connecting Pipes
Connecting pipes shuttle the gas from one part of the exhaust system to another. They are all made of steel. They come in different shapes and sizes, depending on your car’s exhaust system design.
What Causes Exhaust Leaks?
There are many things that could lead to exhaust system leaks. Here is a couple of things you should be on the lookout for.
Corroded Exhaust System Components
Exhaust systems are steel components sitting out in the open. They get very hot. They’re exposed to water, snow, and other types of debris and contamination on the road.
Even though they are made of stainless steel, they will eventually succumb to corrosion working under such harsh conditions.
Over time, the rust eats into the metal. It could be severe enough to puncture holes or gashes in sections of the exhaust system. These weak points will lead to exhaust leaks.
Physical Impacts on the Exhaust System
Not every road is a smooth paved or murram surface. Some roads are full of potholes, rocks, and deep ruts (especially if you offroad a lot.)
All these hazards could damage anything they get to contact with under your car. With the exhaust system being one of the lowest-lying parts of the car, they are most susceptible to gashes and impact.
If your car is low-slung and doesn’t have protective skid plates, inspect it now and then.
You could also make a habit of inspecting the bottom of your car every time you hear it scrap against the ground or an obstacle as you drive.
This will help identify damages to the exhaust system and other critical components that sit under the car before it is too late.
Old Failing Gaskets
Gaskets go between connecting pipes and components in the exhaust system. For instance, there is a gasket between the exhaust manifold and the engine.
The gasket’s work is to form a perfect seal between components. However, over time, they degrade and start creating uneven surfaces.
If this happens, you will have small or massive leaks depending on the damage.
Some other joints in the system don’t have a gasket. However, they need clean surfaces and tight bolts to form a perfect seal. A leak between these joints only happens if your exhaust system was disassembled recently and wasn’t properly screwed together.
Bad Welds on the System
A great deal of exhaust system repairs involves welding. Welding isn’t as straightforward as we think – especially if they have to be air-tight.
Bad welds on custom exhaust systems or after a repair job could lead to exhaust leaks.
Old Components
Lastly, everything in a car wears out. When they do, they form bad seals or are less perfect. Manifolds will fail, mufflers will grow brittle and catalytic converters will leak.
At this point, you have to overhaul the entire system. By the time it happens, chances are your car is already very old and perhaps it’s time to replace it.
How to Find an Exhaust Leak Fast
Now that we know where leaks can occur pinpointing them sounds easy. Finding those significant leaks is simple. However, things get more complex when the leaks are not obvious or are hidden away. Here are some tips to help you pinpoint harder to hear, feel or see leaks.
Block the Exhaust to Amplify the Leak
Sometimes, hearing or seeing the leak can be challenging. You can amplify its effect by increasing the backpressure to your car’s engine.
To do this, you will have to block the exhaust system’s outlet. Get some rag and stuff it into the exhaust outlet. Remember to keep part of it hanging out so that you can pull it out.
Start the car and quickly go over your entire exhaust system listening or looking for the leak. The backpressure will force exhaust gases to leak out through another avenue hence making it easier to see.
Don’t keep your exhaust plugged for long, though. Move fast, narrow down the leak and switch off your car. Don’t forget to unblock the exhaust.
Use an Automotive Smoke Machine
Professional mechanics can invest in an automotive smoke machine to help them identify leaks.
This is a machine that generates and sends compressed smoke through the exhaust system. If there is a leak, you will see the smoke seeping out through the problem areas.
Try Some Soapy Water
A simple but effective way to check for a leak is spraying potentially problematic parts of the exhaust system.
Do this on a cold engine as you don’t want the soapy water to evaporate away before you can observe.
Have someone crank up the car as you observe a problematic area. If there is a leak there, you will see the soap bubble up or foam before it drying up as if something is blowing through it.
How Do You Fix Exhaust Leaks
The fix will depend on where the damage is. If it is at a gasket, it could be as simple as opening up the exhaust and replacing the gasket.
If a pipe is damaged, you could weld it or fabricate a new one to replace the damaged pipe.
Things get more complex when the damage is on expensive component seals or surfaces like the resonator, catalytic converter, and muffler.
In this case, you might have to replace the damaged part or hire a very skilled welder to plug the hole.
Simple fixes like using a sealant, tape, or putty are temporary. You will need to replace the damaged part or get an expert to weld the holes shut (if they are on a surface that can be welded)
Can You Drive a Car With an Exhaust Leak?
While a car with an exhaust leak is still drivable, it is an obnoxious health hazard. To start, it will be louder than it should be. The noise pollution will annoy you, your passengers, and other road users.
Secondly, carbon monoxide and other dangerous combustion byproducts will leak into the cabin. Sustained exposure with poor ventilation (windows closed) will make you drowsy at first and could even lead to unconsciousness.
A drowsy or unconscious driver cannot be good news on the road. You will cause accidents.
Can an Exhaust Leak Cause Loss of Power?
Your car needs some backpressure for optimal performance. It is tuned to work with a percentage of pressure. While reducing it to small extents might increase power, a severe leak dropping the pressure substantially will affect the engine performance.
Your engine will feel less powerful, and your car will accelerate sluggishly. Moreover, a leak could also lead to dips in fuel efficiency.
Can an Exhaust Leak Cause a Check Engine Light?
It can – if it happens at a monitored section of the exhaust system. For instance, if the leak is at the exhaust manifold gasket, it will offset the upstream oxygen sensor’s readings.
If it is big enough, it could make your car throw a too lean error and light up the MIL (check engine light). If it is downstream (after the catalytic converter), it could make the oxygen sensor readings erratic, making the ECU think the catalytic converter efficiency is below the threshold.
However, a leak at any other point might not throw errors.
What Does Exhaust Leak Smell Like?
An exhaust smell is hard to miss if you’ve lived in a town or have been around engines for a while. It smells like unburned fuel, sulfur (rotten eggs), and other pollutants you smell on the highway.
Check this too: How Do You Calculate Exhaust Size?
It will smell as if you are you have your nose next to the exhaust tips of a slightly old car (New cars with a very new catalytic converter might not smell at all).
Bottom Line
Even though an exhaust leak might not render your car undrivable, fixing it as soon as possible will extend your car’s lifespan and make it more fun to drive. Please don’t wait until the leak gets too big as it might be more expensive to fix by then.